1. Field of the Invention
The present invention relates generally to a receiving apparatus and method of a wideband mobile communication system, and in particular, to an apparatus and method for canceling narrow-band interference contained in a wideband receiving signal.
2. Description of the Related Art
A mobile communication system provides a mobile terminal with a radio communication service using given radio frequency resources. However, in reality the mobile communication system experiences deterioration in performance due to interference which can be generated in radio environments, and may bring about a malfunction. Therefore, technical efforts for canceling the interference are needed.
In general, interference which is generated in the mobile communication system is broadly divided into common frequency interference and near-by frequency interference. The common frequency interference includes interference between base stations using a common (or same) frequency, and interference from other systems such as illegal radio stations. The near-by frequency interference includes interference between base stations using near-by frequencies within the same system, and interference between adjacent systems.
The worst interference in an existing wideband mobile communication system may be powerful narrow-band interference from other systems using a common frequency resource. In a mobile communication base station system, the narrow-band interference may lead to deterioration in system performance and communication interruption. Conventional methods for canceling the narrow-band interference are as follows.
A first method uses a narrow-band interference cancellation filter at an intermediate frequency band. That is, if a narrow-band interference signal is received, a fast interference signal detection receiver detects the interference signal and converts the frequency of the detected signal into an intermediate frequency. The signal converted into the intermediate frequency signal is subject to filtering to remove the intermediate signal and reconverted into the signal having an original frequency. This method has disadvantages of a large-capacity, large-sized apparatus, and relatively high power consumption.
A second method suppresses the narrow-band interference by filtering and fast Fourier transform. That is, a filter is used with respect to an interference signal having high power, and quantization, fast Fourier transform (FFT), and inverse FFT techniques are used with respect to an interference signal having low power. However, this second method is also disadvantageous in that an apparatus is complicated by using different techniques according to the power of the interference signal, and a delay time of a receiving signal is increased by performing the FFT and the inverse FFT.
A third method suppresses the narrow-band interference by using an adaptive digital filter. That is, an input signal at a carrier frequency is subject to frequency-down conversion, gain control, quantization, and conversion to a digital signal. An interference signal is detected from the digital signal. An adaptive digital IIR (Infinite Impulse Response) filter is used to eliminate the interference from the detected interference signal. However, the use of the IIR filter adaptable to the interference signal increases in complexity.